Tristan,
There can almost always be some sort of angle intended. The most obvious of which is the player that mucked his hand and (accidentally?) exposed his cards to his partner.
To answer your question, yes I would always consider suspending the action because, in your original post, one player already acted and there was still action pending. If the hand were exposed before any players acted, then it would be a different situation. The obvious advantage after a player has wagered, is with the player seeing the exposed hand while facing a bet.
I will give you one good example for my reasoning: Three players, final betting round, Player A bets, Player B tosses his hand to the muck and it flips over, (Ace of hearts Queen of spades). Player C now knows that the only hand that could beat his King high flush (he is holding K,J of hearts) was exposed by the exposed hand!